The first Taiko is at 0.66, the sequel is at .29 combined they're at 0.95 but Namco says that the series as crossed the million mark.
The Taiko Drum Master series has topped the million sold mark on the Wii, and Namco Bandai will be celebrating. Not with a third entry in the series, but with a reissue of the first one.
Taiko Drum Master currently has two Wii installments, the original Taiko Drum Master Wii, released in December 2008, and a November 2009 sequel.
The sequel was offered solo and bundled with a drum controller. The original, presumably under the consideration that no one had a drum controller for their Wii (although the game can technically be played without the controller) was offered exclusively in bundle form.
http://www.andriasang.com/e/blog/2010/02/16/taiko_drum_master_million/
So one of the games is undertracked, or maybe both.